Slip forming apparatus and method



Feb. 24, 1970 M. BARRON 3,497,579

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Feb. 24, 1970 M. BARRON SLIP FORMING APPARATUS AND METHOD '7 Sheets-Sheet Filed March 25, 1965 m T m V m Feb. 24, 1970 M. BARRON I 3,497,579

SLIP FORMING APPARATUS AND METHOD 7 Filed March 25, 1965 7 Sheets-Sheet 5 IIIIIIIIIA INVENTOR.

' Feb. 24, 1970 M. BARYRON 3,497,579

SLIP FORMING APPARATUS AND METHOD Filed March 25, 1965 7 Sheets-Sheet e INVENTOR.

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United States Patent 3,497,579 SLIP FORMING APPARATUS AND METHOD Maurice Barron, 291 Ridgeway, White Plains, NY. 10605 Filed Mar. 25, 1965, Ser. No. 442,678 Int. Cl. E04b 1/16, 1/04 US. Cl. 26433 5 Claims ABSTRACT OF THE DISCLOSURE This invention is a slip form apparatus resembling a caterpillar tractor laid on its side, and includes the method of using a continuous flexible belt on rollers as a molding means for building structures of concrete or cementitious materials. It is particularly adapted to long, shallow, slab-like structures such as highway or airport pavement, or to various plan shaped tower-like structures such as chimneys, and underwater structures built automatically from the bottom up to and above the surface of the water.

My invention relates to building construction of the slip form type. More particularly, the invention is concerned with improved apparatus for the construction of concrete structures, structures formed from cementitious construction material and reinforced concrete structures, employing a slip form liner, and to improved methods of construction using a slip form liner to form and mold the construction material.

Heretofore, with conventional methods of slip form construction, a slip form is brought into contact with newly placed plastic concrete. The slip form is filled in layers and moves in a vertical direction upwardly at a slow pace while leaving a space at the top of the slip form for the pouring of more concrete to be placed. As known, portland cement concrete generally hardens quite quickly, changing from a plastic state to a rigid solid state. In the plastic state the concrete exerts pressure in accordance with natural laws of liquids. The rate of travel of the slip form is regulated so that the concrete at the top of the slip form is always placed in a plastic condition, and is in a rigid, non-plastic condition at the bottom of the slip form. Thus, when the bottom of slip form leaves the concrete, the shape of the concrete remains intact and no containing or retaining form is needed.

The conventional apparatus used in slip form construction generally includes yokes, wales, sheathing and jacks. The yokes serve two primary functions: one is to keep the forms from spreading, so as to resist liquid pressures, and the other is to transfer the loads imparted to the forms to the jacks. The wales stiffen the forms and are braced to carry the load to the yokes. Finishers scaffolds and a Working deck are usually connected to the wales, the Wale-yoke connections being designed to withstand these loads. The sheathing is attached to the wales in a vertical position so as to cause a minimum drag. In many instances the drag load is greater than the weight being lifted. A conventional method of raising the slip form is to provide several small lifting jacks attached to smooth vertical round jacking rods; the steel rods on which the jacks climb are specially designed for this purpose. The jacking rods are braced by the concrete, and the rods may be salvaged for re-use. The lifting jacks are securely attached to the yokes, and the load carried by the yokes is the weight of yokes themselves and loads supported by the assembly such as equipment and workmen, together with the drag between the sheathing and concrete. There are many factors and variables which affect the construction using conventional slip form apparatus. Some of the factors and variables are the rate ice of movement, the slump or wetness of the concrete, the ambient temperature, the rate of filling the form, the manner of vibrating or manipulating the concrete in the slip form, the moisture in the aggregates, the humidity, the fineness and uniformity of the cement, the mixing time in the mixing truck, the thickness of the construction, the depth of the slip form, the tightness of the slip form, the location and amount of the reinforcement, the type and condition of the contractors equipment, delays in delivery of concrete, the breakdown in equipment, and others.

These factors and variables are so numerous and complex that their control is practically impossible and, therefore, many disadvantages result in addition to several limitations, some of which are:

(a) The drag caused by the slip form sliding over the concrete is large and frequently exceeds the weight being supported and lifted. The power required is therefore large and many jacks of high capacity are required.

(b) The appearance of the surfaces of the concrete is objectionable, leaving many horizontal streaks, bands of discoloration, honeycombing, and surface defects due to tearing, ripping and leaky forms.

(0) The control of the plasticity and strength of concrete is very exacting and costly.

(d) While vertical fluting is possible, no horizontal fluting, sculpturing, or surface pattern can be accomplished.

(e) No surface texture other than the exposed and aesthetically undesirable surface of the concrete is possible. Therefore, to improve the appearance, costly rubbing, finishing, plastering and often painting is required.

It is therefore an object of my invention to provide methods and apparatus for better control of the factors and variables in slip form construction which affect the quality, the speed of construction, and the cost of the operation, and the appearance of the finished construction.

Another object of my invention is to provide improved methods of using movable forms and in particular, methods of using movable forms in combination with a liner to provide various surface configurations not possible heretofore with facility in slip form construction.

Yet another object of my invention is to provide improved apparatus including movable forms in com bination with various liners to form with facility wall structures, columnar structures, hollow structures, building structures and other types of continuous outer surface and discontinuous outer surface structures.

Also, my invention makes possible several new shapes for construction, which shapes are not possible at all, or are very costly with conventional methods and conventional equipment. Another object of my invention is to make possible a variety of surface color and surface texture for movable form construction and for the more conventional non-movable form concrete construction, and the impressing into the surface any desired pattern or sculpture. Another object is the automation of the operation both for underwater construction and dry land construction which lowers the cost and improves the end product.

Other objects, advantages and features of my invention will be self evident to those skilled in the art as the more detailed description thereof proceeds.

FIGURE 1 is a schematic representation, partially in vertical section, taken along line 11 on FIGURE 5, of a movable form in combination with a rigid type of form liner in accordance with the invention.

FIGURE 2 is a sectional view taken along line 22 on FIGURE 1.

FIGURE 3 is a sectional view taken along line 33 on FIGURE 1.

FIGURE 4 is a sectional view taken along line 44 on FIGURE 1.

FIGURE 5 is a schematic representation, partially in section, of the end portion of the movable form.

FIGURE 6 is a detailed schematic representation of sheathing of the slip form apparatus having thereon the surface of a form liner and illustrating a facing for the formation of a particular pattern.

FIGURE 7 is a sectional detail view taken substantially along line 7-7 on FIGURE 6.

FIGURE 8 is a detail view, in section, of the sheathing having a composite liner including a form liner and an inner liner providing a facing for the composite liner to provide a particular surface facing for the construction.

FIGURE 9 is a detail view, in section, of the sheathing with a non-removable form liner which form liner is to remain embedded in the construction.

FIGURE 10 is a schematic representation, partially in vertical section, of a modification of the invention.

FIGURE 11 is a sectional view taken along line 1111 of FIGURE 10.

FIGURE 12 is a sectional view taken along line 1212 of FIGURE 10.

FIGURE 13 is a sectional view of a form liner with an insulating liner.

FIGURE 14 is a sectional view of a form liner with a patterned inner liner.

FIGURE 15 is a view in elevation and partially sectional view of an opening in the construction.

FIGURE 16 is a sectional view taken along line 16-4 of FIGURE 15.

FIGURE 17 is a sectional view taken along line 1717 of FIGURE 18.

FIGURE 18 is a sectional view taken along line 1818 of FIGURE 17.

FIGURE 19 is a view, partially in section, of a liner with saddle shaped rollers in a straight alignment.

FIGURE 20 is a view, partially in section, of a liner with barrel shaped rollers in a straight alignment.

FIGURE 21 is a view, partially in section, of a liner with saddle shaped rollers in a curved alignment.

FIGURE 22 is a view, partially in section, of a liner with barrel shaped rollers in a curved alignment.

FIGURE 23 is a view, partially in section, of a pair of liners, one with saddle shaped rollers and one with barrel shaped rollers, in a curved alignment.

FIGURE 24 is a view, partially in section, of a pair of liners with cylindrical shaped rollers, in a curved alignment.

FIGURE 25 is a plan view of the developed shape of 3 pieces of form liner.

FIGURE 26 is a diagrammatic representation of a form liner and an idler pulley.

FIGURE 27 is a view, partially in section, of a form liner and a steel plate insert carried by the form liner.

FIGURE 28 is a view, partially in section of a form liner and a structural shape insert attached to the form liner.

FIGURE 29 is a view, partially in section, of form liner and a built up structural shape insert attached to the form liner.

FIGURE 30 is a schematic representation, partially in vertical section, of another modification of the movable form in combination with coiled reinforcement.

FIGURE 31 is a schematic representation, partially in vertical section, of another embodiment of the invention.

FIGURE 32 is an enlarged detail of a portion of FIG- URE 31.

FIGURE 33 is a view, partially in section, taken on line 3333 of FIGURE 32.

FIGURES 34 and 35 are enlarged details of portions of FIGURE 31.

Referring now, more particularly, to the drawings, in which like characters of reference designate corresponding parts throughout, one embodiment of the invention which is especially well adapted for slip form construction is shown in FIG. 1 and comprises of form liner 24 and a movable form system which includes a plurality of yokes 2, a plurality of lifting devices or jacks 4, and jacking rods 6. Each yoke 2 has a horizontal member 8 and two vertical legs 10 which may be permanently and rigidly attached to the horizontal member 8 or they may be adjustable, and for this purpose toggle joints 12 and turnbuckles 14 are provided, and adjustment may also be obtained by shifting pins 16 with respect to the group of holes 18 provided in yoke 2. Adjustment of the vertical legs 10 may be obtained by spreading them to any desired position by means of the toggle joints 12 and turnbuckles 14. Pins 16 are provided to couple the turnbuckles 14 to the yokes 12 and holes 18 which are provided for adjustment, and which may be effected by shifting the pins 16 to another of the holes 18. After the toggles 12 and turnbuckles 14 are adjusted, the desired position may be secured by means of wedges 20. With this type of adjustment, the dimensions of the finished concrete structures may be varied so that the thickness, the width, the length, or any combinations of these dimensions, may be altered to obtain any desired structures. The lifting jacks 4 are fastened to the yokes 2 and climb up the jacking rods 6. As the lifting jacks 4 pull themselves up the jacking rods 6, the yokes 2 and everything attached to them also move up. The lifting jacks 4 may be powered hydraulically, electrically, mechanically or manually. The jacking rods 6 may be salvaged for reuse by encasing them in thin tubes 21 or they may be left embedded in the concrete 22 to act as reinforcement. For convenience and clarity, the embedding of the reinforcing rods in the concrete are not shown in the figures.

In FIGURES 1 to 9, the movable form system is shown in combination with a rigid type of the form liner 24 in operative position in contact with concrete 22. Sheathings 28 are connected to the vertical legs 10 by means of wales 30 to position the form liners 24 and to control the dimensions of the concrete. The form liner 24 is smooth on the outside and may be smooth on the inside or have projections or moldings 26 which project into the concrete 22 and produce a sculptured effect on the outer surface of the hardened or set concrete in desired patterns. Projections 26 may be formed as an integral part of the form liner 24 or may be removable. The form liner 24 is provided in sections which are fed in at the top where the concrete is poured to form the structure and stripped from the concrete 22 at point a, at which point the concrete is hard or has hardened sufliciently to achieve its permanent shape. The stripped sections of the form liner 24 may be cleaned and reused.

The concrete 22 is plastic near the top and exerts a hydrostatic pressure which is transmitted through the form liner 24 to sheathing 28. The sheathing 28 holds the form liner 24 in place and its itself held in place by wales 30. The wales 30, in turn, transmit the reaction from the pressure to the vertical legs 10 of the yokes 2. The horizontal pressure is finally transmitted to the horizontal cross member 8 of the yoke 2. Braces 32 are connected to the wales 30 to strengthen the wales 30 and help to transfer the load from the wales 30 to the yoke 2.

In order to insure that the form liner 24 remain in contact with the concrete 22 and not move with the sheathing 28 which is moved by the movable form sys tem, sliding takes place between the outside of the form liner 24 and the inside of the sheathing 28. In order for sliding between the sheathing 28 and the form liner 24 to take place, it is necessary to overcome the frictional re sistance of sliding between these surfaces. Furthermore, for certain purposes sliding between the two surfaces is to be increased as this is accomplished by lubrication. As the movable form system moves up, additional sections are added to the form liner 24 and more concrete 22 is placed in the form. Lower sections of the form liner 24 not in contact with the sheathing 28 may be removed from the concrete 22 after it has appropriately set. Working platforms 33 may be supported as shown on FIGURE 1, or supported by the horizontal member 8 of the yoke 2, or supported on an upper framework attached to the yokes 2. Hangers 34 are attached to the vertical legs 10 of the yoke 2, and these hangers 34 support a platform for workmen who smooth out any rough spots in the concrete surface below point a.

An important feature of this invention is the provision of a form liner 24 which remains in position relative to the concrete 22 until the concrete 22 has hardened. Thus, instead of the form sliding along the concrete, the slipping takes place between the form liner 24 and the sheathing 28. Thus, all the advantages of conventional cast-in-place concrete are secured in movable form construction. More over, if the sheathing 28 were to be placed into contact with the concrete, the rate of movement would have to be decreased or the length of the sheathing 28 increased.

Referring now more particularly to FIGURE 5 which shows how the movable form is arranged at the end and corners of a structure during the construction. It will be noted that the movable form systems of the type shown in FIGURE 1 are shown in order to cast the end, two corners and two adjacent sides. While only three movable form systems have been shown, it is evident that, depending upon the length of the walls to be made, any number of movable form systems may be supplied to form any desired wall size.

Referring now more particularly to FIGURE 6 and FIGURE 7 which show a form liner 24 with a pattern of pyramidal projections 26 in order to provide the surface of the concrete 22 in a desirable pattern with a pyramidal depression type sculptured effect. In this embodiment the form liner is formed as a unitary member.

In FIGURE 8, there is shown amodification of the form liner, which comprises an inner form liner 36 positioned against a base form liner 24 provided with smooth surfaces for economy, change in pattern or ease of construction. It will be evident that the composite form liner formed of the base form liner 24 and inner form liner 36 is particularly useful where the pattern on the outer surface of the structure is to be changed.

In FIGURE 9, there is shown a modified form liner 38 which is intended to be left in place in the construction or structure upon completion to serve as a facing for the concrete 22.

Referring now more particularly to FIGS. 10 to 12 which illustrate a modification of the rigid form liner 24. In FIGS. 10 to 12, the form liner 24 instead of being rigid is provided as a continuous flexible belt liner 40 which is supported by, and moves around, a plurality of frames 42. A frame 42 is carried by each of the two vertical legs 10 for positioning a plurality of rollers 44, 46. Instead of sliding along sheathing 28, the movable form rolls on the rollers 44, 46. The rollers 44 are provided to resist pressure and are so spaced that the belt liner 40 is permitted to bulge slightly near the top of the concrete 22. As the movable form moves up, the concrete in the bulges is subjected, by the moving rollers 44, to a kneading, squeezing or puddling action which is high- 1y desirable, since this action improves the texture of the surface of the concrete by forcing the laminar material into the plastic concrete. The spacing of the rollers 44 near the lower part of the mechanism is close together in order to prevent bulges and to hold the material to the final desired shape. The rollers 46 do not resist pressure from the concrete but are for the purpose of guiding the belt liner 40. The belt liner 40 is smooth on inside where it is in contact with the rollers 44. On the outside of the belt liner where it will be in contact with the concrete 22, the belt liner 40 may have attached to it any desired pattern of molding projections 26, such as shown in FIG- URES 6 and 7 or FIGURE 8, which will shape and sculpture the surface of the concrete 22. These projections 26 may be an integral part of the belt liner 40, or they may be attached and detachable. Moreover, it is also possible for the flexible belt 40 to be provided in the form shown in FIGURE 9 so as to form a facing and for this purpose the form liner may be formed with the projections shown on form liner 38. The pattern of impressions can repeat itself, or changes in the impressions may be made by attaching other shapes in place of projections 26.

In order to protect the belt 40 and rollers 44, 46 from dirt and debris, a plurality of sheet metal pans 48 are provided which are held in place by the frames 42, see FIGURE 10. A shield 43 is placed around and is somewhat removed or spaced from the frame 42 and belt 40. The shield 43 serves as a housing for the belt and frames. In this -way the equipment is sheltered from the elements such as wind, rain and sun. Also, when the ambient temperature is low, a heater can be installed within the shield 43 so that the curing of the concrete can be accomplished at desirable temperatures. The rollers 44 transmit the pressure due to the plastic concrete 22 from the belt liner 40 to frames 42 which are restrained by the wales 30. The wales 30 transfer the horizontal reactions from the wales 30 to the vertical legs 10 of the yokes 2. The wales 30 are attached to the vertical legs 10, and transfer the vertical loads from the wales 30 to the vertical legs 10, then to the horizontal member 8 and finally to the jacks 4, and jacking rods 6. Struts 50 are connected to the frames 42 and serve to brace the frames 42, wales 30, and vertical legs 10. As the jacks 4 move up lifting the moving form, the belt liner leaves the concrete 22 at point b where the concrete 22 is rigid and no longer requires 8. containing form.

Another important feature of my invention lies in method and apparatus for providing surface texture to the concrete or outer surface of the structure. For this purpose, a hopper space 52 is provided which is positioned between the belt liner 40 and a hopper wall 54. Hopper wall 54 extends into the plastic part of concrete 22. The hopper space 52 may be filled with various materials, such as stone chips 56, colored mortar, masticmaterial, glass beads, plaster, etc. The throat of the hopper space 52 which is the space between the belt 40 and hopper wall 54 is adjusted to provide the required thickness of coating. The hopper 52 may also be filled with a construction material which has physical properties, such as plasticity, density, strength, etc., different from that of the interior construction material 22. This will result in a laminated construction with controlled adhesiveness between the laniinations. The belt liner 40 and the pressure from the rollers 44 manipulate the material 56 from the hopper space and assist the material in entering into the concrete 22 while the concrete 22 is still in its plastic condition. When the concrete 22 is hard, as at point b, the hopper material 56 is then an integral part of the mass. Thus, the interior of the construction is ordinary construction mate rial, such as concrete 22, and the surface has the desired color, texture and form.

When the width of the concrete 22 is large, several yokes 2 are required. With fewer yokes 2, the span of the wales 30 will be larger making the strength and size of the wales 30 impractical. Since the belt liner 40 revolves and must pass the vertical legs 10 of the yokes 2, a split or slit 41 is provided in the bell liner 40 as best seen in FIGURE 11. The slit 41 has a mouth shaped opening which is provided in order to by-pass the vertical legs 10. At the mouth shaped opening of slit 41, the belt liner 40 is folded back and returns to its normal position after the by-pass. A metal guide may be furnished to fold and guide the belt liner 40 around the opening. The two parts of the belt liner 40 on the sides of the slit may be joined automatically as described in my previous Patent No. 2,509,195 providing the required by-pass opening. Where required, similar openings are provided in the belt liner 40, to by-pass the hangers 16 for the finishers scaffold.

As best seen in FIGURE 12, cylindrical rollers 44, 46 fit into bearing blocks in the frames 42. The frames 42 are spaced close enough to make the length and diameter of the rollers 44, 46 practical.

In FIGURE 13, there is shown the manner in which insulation may be applied to a concrete surface by use of an insulating liner 58 held in place by the belt liner 40, Or by the form liner 24. If the insulating liner 58 is rigid enough it may be used in place of the form liner 24. In this case, the sheathing 28 slides on and along the insulating liner 58.

A separate inner form liner 60, between the concrete 22 and the belt liner 40, is shown in FIGURE 14. The inner liner 60 may have a varied and interchangeable pattern and may be fed from a roll attached to the yoke 2.

FIGURE and FIGURE 16 illustrate how openings of any size, such as door and window openings, may be formed. A frame 62 may be adapted to fit between the belt liners 46. When the concrete 22 hardens, and the belt liners 40 have passed the frame 62, the frame 62 is removed leaving the required opening.

In the conventional slip form apparatus use is made of jacks 4 and jacking rods 6 to lift the slip form. A feature of my invention is represented in FIGURE 17 which shows a new and better mechanism for lifting the movable form.

The form liner 64 may be either the rigid form liner 24 or the flexible belt liner 40 having projections on both sides of the form liner. The projections 66 engage the form liner 64 to the concrete 22. The projections 68 engage two or more pinion gears 70 which are power driven to lift the mechanism. The engaging pinion gears 70 are located such distance below the top of the concrete 22 that the concrete 22 has adequate strength and the form liner 64 is long enough to properly develop support through projections 66 bearing on the concrete 22. If required, internal ties 72, which are provided with snap releases, may be used to insure both dimensional control and to provide added strength for the form liner 64. The width of projections 68 are only a little wider than the teeth of pinion gear 70. The outside of the form liner 64 between projections 68 is smooth and supported laterally by the sheathing 28, or by the rollers 44.

FIGURE shows a wedge shaped piece 78 of form liner inserted between two pieces of trapezoidal shaped pieces 80 of form liner. When this combination of pieces is used in the movable form, a variable dimensioned shape of construction will result. That is, as the movable form moves up, the width of construction will increase uniformly. The rate of increase will depend on the size of the apex angle shown on FIGURE 25. If the wedge shaped pieces '78, 80, of form are inverted with the apex angle at the top, the width of construction will reduce at a uniform rate. If these shaped form liners are used with circular shaped movable forms, the result will be conic sectional construction similar to the shape of a morning glory flower. In a similar manner any shape structure may be constructed by using form liners which are devel oped surfaces of the desired construction. Using the ad justa-ble yoke 2 as shown in FIGURE 1, and by properly adjusting the rate of spread using the toggle joints 12, the turnbuckles 14, and by slanting the vertical legs 10, the thickness of the construction may be varied at any desired rate, either thicker or thinner.

FIGURE 26 illustrates the addition of an idler pulley 82 to the moving form. The belt liner moves around the frames 42 and also around the idler pulley 82. By adjusting the position of the idler pulley 82. the tension in the belt liner 40 may be adjusted. The distance 0 to d between the top of the concrete 22 and the bottom of the belt liner 49 may also be regulated by changing the posi- An important feature of my invention is a simplified method and means of combining concrete construction with structural steel construction. Such a combination has the advantages of the best features of the two structural systems and also overcomes many of the disadvantages of each system. This will not only greatly reduce the cost of construction but will also speed up the construction. To accomplish this, structural steel connecting inserts are held in place by the form liner and are thus imbedded in the concrete. To these steel inserts are later attached structural steel members. Thus, in FIGURE 27, a steel plate 84 is shown adhesively coupled to the belt liner 40. The steel plate 84 is anchored into the concrete 22 by means of steel straps or reinforcements 86. After the concrete 22 hardens the belt liner &6 is pulled apart from the steel plate 84. In FIGURE 28 is shown a T-shaped structural steel insert 88 used in a similar manner. FIG- URE 29 shows a built up structural steel insert fit) made from a steel plate 92 and two steel angles 94. The steel angles 24 are separate by a gap which is filled by a removable part of the belt liner 40. After the belt liner 40 has passed the insert and removed the plug between the steel angles 94 a structural steel beam 96 is attached by inserting the web of the beam 96 into the gap between the steel angles 94. The web of the steel beam 26 bears on the steel plate 92. The steel beam 96 is connected to the insert 90 by means of bolts 98 and nuts 99 which are spot welded to the steel angles 94. For convenience, the strap anchors 86 are not shown in FIGURE 29. Welding may be substituted for bolting in attaching the structural steel shapes to the steel inserts. It should be noted that in the present state of the art, using conventional slip forms, there is no way of holding an insert in place accurately. Tying the insert to the reinforcement has been tried but has not worked satisfactorily.

FIGURE 30 shows how the movable form may be automated, and which may be especially useful for underwater construction. The movable parts may be self-contained and, together with the plastic construction material, shielded from contamination by any deleterious substance. Internal vibrators 102 are positioned in a pattern and attached to the movable form. External form vibrators 1 04 are attached to the frame and transmit their vibration thru the rollers 44, thru the belt liner 40 to the surface of the concrete 22. An automatic timing device can operate vibrators 102 and vibrators 104 to result in scientific vibration rather than the haphazard vibration now used. Also, reinforcement may be placed automatically and exactly by use of spring coil welded wire fabric 106 which is mounted on the vertical legs 10 and guided into the concrete 22 by means of pulleys 108 and metal guides 110. By providing a brake or clamp to the coil 106 tension in the longitudinal wires 112 of the coil 106 will provide prestressing of the concrete 22. The present state of the art of prestressed concrete provides methods of transforming the prestress force to form the reinforcing steel to the concrete. One method holds the reinforcing in tension in a clamping device while placing concrete around the stretched reinforcement and after the concrete has hardened, the clamps are released permitting a relaxing of the ends of the stretched reinforcement thereby transferring the load from the clamps to the concrete inducing a state of. compression in the concrete. A second method is to separate the reinforcing tendons from the concrete by placing the reinforcing tendons in tubes or precast holes to prevent the concrete from bonding to the reinforcing tendons. After the concrete has hardened the reinforcing tendons are stretched by jacking against bearing plates which push against the concrete. The stretched reinforcing tendons are clamped against the bearing plates creating an induced compression in the concrete. In the present state of the art the tension in any tendon is constant and the prestressing force is equal to the sum of the tensions of all the tendons at a cross.

My invention makes possible a variable prestressing of the concrete by providing a variable stress along the tendon. This is accomplished by varying the braking force applied to the coil 106 as the construction advances. Thus, if greater prestressing is desirable, or required by design, at the bottom of the construction and less prestressing is required at the top of the construction, the braking force is reduced uniformly on in steps as required. The braking force thus adjusted and controlled is transmitted to the longitudinal wires 112 at varying amounts. The concrete 22 hardens around the stretched reinforcement and the decrement in the braking force will be the decrement in the amount of prestress that the reinforcement delivers to the concrete. This, I call, variable prestress which is a new term added to the art and science of concrete construction. Since it is desirable, in prestressed concrete, to have a high yield point for the steel reinforcement, and since welded wire fabric has a relatively low yield point, separate coils of high yield steel wire, or strands of such wire, may be added to produce the desired prestress. These added coils may be installed in a tandem position, by means similar to the means for installing coils 106. A hopper 114, with an adjustment for height of hopper, supplies concrete 22 to the belt liner 40 at a controlled rate.

FIGURES 31, 32, 33, 34 and 35 show a preferred embodiment of the invention wherein an entirely different means of lifting the equipment is disclosed. Instead of lifting jacks 4 and jacking rods 6, the yokes 2 are pushed up by means of hydraulic, telesopic cylinders 116 and 118. The cylinder 116 slides inside cylinder 118. Cylinder 116 is attached to the insert 90, 94 (see FIGURE 29) by means of a structural clevis 120. The attachment is made with cylinder 116 retracted into cylinder 118. After attachment the cylinders 116 and 118 are extended by hydraulic pressure and the extension pushes up the yoke 2 the legs 10, the frame 42, etc. The attachment at the bottom of the cylinder 116 is made at a level of the concrete 22 where there is adequate strength. A cylinder 122 has a length such that when cylinders 116 and 118 have a proper extension, cylinder 122 can be pushed up until hole 124 matches hole 126 and the cap plate 128 of cylinders 122 comes in contact with a cap plate 130. Hole 124 is in a lug. 133 which is part of the cylinder 122. Hole 126 is in a structural clevis 134 which is identical to the structural clevis 120. A pin 136 (not shown in figures) is inserted and secured in the holes 124 and 126. This secures the cylinder 122 to insert 90, 94 thru the clevis 134 which is attached to the insert 90, 94. The connection of clevis 120 and 126 are similar to the connection shown in FIGURE 29 and are not repeated for clarity in FIGURES 31, 32, 33, 34 or 35. After the pin 126 is in place and the cap plates 128 and 130 are almost in contact, the cylinders 116 and 118 are slightly retracted, thereby transferring the load from cylinders 116 and-118 and from the clevis 120 and from the insert 90, 94 attached to the clevis 120, to the cylinder 122, and to the clevis 134 and to the pin 120 and to the insert 90, 94 attached to the clevis 134. Then the clevis 120 can be detached from its insert 90, 94, and the cylinder 116 can be retracted until the clevis 120 reaches and is attached to insert 136. Extension of cylinders 116, 118, under hydraulic pressure, then transfers the load from cylinder 122 back to cylinders 116 and 118, and from insert 134 to insert 136. The cycle of extension, load transfer, and retraction is repeated as many times as required. As a safety measure, the pin 126 is not pulled until cylinders 116 and 118 are extended and cylinder 122 is ready to be raised. Dependent on the amount of load to be lifted, intermediate yokes may be used with hydraulic jacks 4 or hydraulic cylinders 116, 118. These intermediate yokes are lifted by being supported'on a cross 'beam which is attached to power activated yokes 2. For clarity, connections are not shown in FIGURES 31, 32, 33, 34, 35. These are standard connections as shown as pins 16 in FIGURE 1, as bolts 98 and nuts 99 in FIGURE 29 but other standard means of attachment such as welding may be used.

It will be evident that it may be necessary to stop the vertical member construction for many reasons. For this purpose, a retarder may be added to delay the setting of the construction or cementitious material so as to directly relate the rate of setting of the material to the rate of vertical movement of the apparatus or construction of the member. It is also possible to use an accelerator to speed up the construction.

It should be understood that, while the figures and specification heretofore describe a vertical movement of the equipment, horizontal movement is equally feasible and is claimed as part of this invention. Thus, in FIGURE 10, the rollers 44 and 46 would be turned and would be vertical instead of horizontal, the frames 42 would be horizontal instead of vertical, and the equipment be moved along by horizontal pushing or horizontal pulling as by a cable. It should be further understood that the apparatus shown in FIGURE 30 and described in these specifications is uniquely suitable and adaptable to underwater construction. The apparatus may be immersed in water, lowered to the bottom to rest on a prepared base or on suitable firm bottom and construction started by placing concrete through the funnel and hopper 114. Furthermore, when soft material is encountered at the bottom of the water, the weight of the construction, as the construction progresses, will sink the entire construction through the soft material until firm material is reached.

What I claim is:

1. A method of constructing wall-like members or other structural elements comprising the steps of positioning molding members between holding means and construction material, pouring the construction material in plastic form between the molding members, moving the holding means relative to the molding members at a rate related to the rate at which the material solidifies while maintaining the molding members in contact with the material in plastic condition to form a finished molded member with a surface complementary to the surface of the molding members, and removing the molding members out of contact with the structural element as the construction material solidifies; wherein the molding members comprise flexible molding means movable .on rollers, and comprising the steps of moving the rollers in a direction transverse to the direction of movement of the molding members in contact with the construction material so as to squeeze, knead or puddle the plastic material to produce a sculptured effect on the outer surface of the structure.

2. A mold assembly for casting wall-like members or other structures of cementitious or like material in situ, comprising a mold having two opposed molding members spaced apart so that a structural element may be cast between them, means holding the molding members in a fixed position relative to the structural element being cast, means for pouring construction material in plastic condition into the space between the two molding members, means for slidably moving said holding means along said molding members progressively as the construction material solidifies, and the molding members being capable of being stripped from the solidified construction material to provide a finished structure; wherein the mold comprises flexible opposing molding members and rollers arranged for movement in a direction transverse to the direction of movement of the molding members to exert a squeezing or kneading action on the plastic construction material to produce a sculptured surface on the structure as the molding members are moved progressively out of contact with the solidified portions of the construction material.

3. A mold assembly for casting wall-like members or other structures of cementitious or like material in situ, comprising a mold having two opposed molding members spaced apart so that a structural element may be cast between them, means holding the molding members in a fixed position relative to the structural element being cast, means for pouring construction material in plastic condition into the space between the two molding members, means for slidably moving said holding means along said molding members progressively as the construction material solidifies, and the molding members being capable of being stripped from the solidified construction material to provide a finished structure; wherein the flexible molding members are movable about an idler pulley which may be adjusted in various positions relative to the molding members so as to vary the contact area of the molding members on the structural element being cast.

4. A method of underwater construction of wall-like or other structural elements comprising the steps of underwater positioning of a mold assembly, pouring plastic construction material through means for pouring plastic material between spaced molding members, vibrating and compacting the plastic material, moving the means for holding the molding members progressively as the construction material solidifies, moving the molding members progressively out of contact with the solidified portions of the construction; wherein the molding members comprise flexible molding means movable on rollers, and comprising the steps of moving the rollers in a direction transverse to the direction .of movement of the molding members in contact with the construction material so as to squeeze, knead or puddle the plastic material to produce a sculptured effect on the outer surface of the structure, removing the molding members out of contact with the structural element progressively as the plastic material solidifies.

5. A method of constructing shallow slab-like or other structural elements comprising the steps of positioning a mold assembly, simultaneously feeding coiled reinforcement into the plastic construction material, pouring plastic construction material between spaced molding members, vibrating and compacting the plastic material, moving the means for holding the molding members progressively as the construction material solidifies, moving the molding members progressively out of contact with the solidified portions of the construction; wherein the molding members comprise flexible molding means movable on rollers, and comprising the steps of moving the rollers in a direction transverse to the direction of movement of the molding members in contact with the construction material so as to squeeze, knead or puddle the plastic material to produce a sculptured efiect on the outer surface of the structure, removing the molding members out of contact with the structural element progressively as the plastic material solidifies.

References Cited UNITED STATES PATENTS 870,881 11/1907 Ham. 1,193,484 8/1916 Ellert. 1,917,062 7/ 1933 Reinhard 24915 1,947,941 2/ 1934 Jackson. 2,004,462 6/ 1935 Bush. 2,096,159 10/ 1937 Brynoldt. 2,411,317 11/1946 Day et al. 2,442,7 3 8 6/ 1948 Whittenberg. 3,039,164 6/ 1962 Kemeny et al. 1,894,676 1/1933 Dresser. 2,806,277 9/ 1957 Hand et al. 26434 2,816,323 12/1957 Munger 264-2S5 3,239,913 3/1966 Richmond 26434 3,245,648 4/ 1966 Johansson et al. 26433 FOREIGN PATENTS 839,701 5/1952 Germany. 1,110,989 10/1955 France.

655,017 7/ 1951 Great Britain.

ROBERT F. WHITE, Primary Examiner K. I. HOVET, Assistant Examiner US. Cl. X.R. 

